In order to increase optical signal bandwidth, optical communications are sent over fiber optic communication lines as wavelength multiplexed signals. For example, a 100G LR4 optical transceiver signal consists of 4 wavelengths separated by 800 GHz traveling on a single fiber. Each wavelength signal is modulated at 25 Gbps so that when they are combined they provide a composite 100 Gbps signal. When received at its intended destination, the optical signal is demultiplexed into its individual wavelengths and then converted to respective electrical signals using photodiodes.
A typical optical transceiver demultiplexes the combined signal using thin film filters with pass bands that are separated by 800 GHz. Once demultiplexed, the different wavelengths that were combined to form the composite signal are steered to a wavelength specific photodiode using actively aligned mirrors. Other demultiplexers utilize Indium Phosphate semiconductor devices which can double as both a demultiplexer and a photodetector. Unfortunately, the Indium Phosphate devices experience high insertion loss, and must be kept at high temperatures due the high temperature dependence of the Indium Phosphate semiconductor material.